The other way around. A collective noun can be concrete; e.g., put the pack (of cigarettes) on the table, but the distinction concrete v. abstract doesn't define that category of nouns. That is, whether a collective noun is concrete or abstract isn't an issue. It's whether a collective noun agrees in number with its verb that's important.
Originally Posted by atm
Note on why nouns are categorized.
All nouns fall into one of these three categories:
Concrete: if you can't touch it, it's not concrete. Punctuation
Abstract: if you can touch it, then it's not abstract.
Collective: make sure it agrees in number with its verb.
All nouns are either proper or common:
Proper: capitalize it.Grammar (morphology)
Common: don't capitalize it.
All nouns are either count or non-count:
Count: add -s
Non-count: don't add -s